Turning apparatus usually use turning bars and, if necessary, also a deflection roller. The textbook, A. Braun: "Atlas des Zeitungs- und Illustrationsdruckes" ("Atlas of Newspaper and Magazine Printing"), Frankfurt/Main (Fed. Rep. Germany), 1960, pp. 62, 63, describes a turning arrangement which has two turning rods or bars which are located in crossed position. A run-on or arriving portion of a traveling web is deflected by 90.degree. by a first turning rod. The web is then passed about a deflection roller, to be deflected by 180.degree. and, then, is again deflected by a second turning bar by 90.degree.. The result will be that the run-off or delivered web portion can be laterally offset with respect to the arriving portion. The respective sides, upper side and lower side of the web, however, are reversed in the arriving and delivered portion, in other words, the web has been turned over. For printed subject matter, that means that prime printing on the arriving portion will appear on the verso side of the web. By shifting one of the turning rods transversely to the arriving web portion, a lateral offset can be controlled, with certain limits. For certain types of paper handling and production of printed material, turn-over, or interchange of the prime and verso sides of the web, upon turning and, if desired offsetting, is undesirable.
The referenced literature, on page 62, further describes an arrangement in which two parallel turning rods are used, which deflect the arriving web twice by 90.degree., each time, so that the delivered web, or run-off web portion, will have the same side arrangement as the arriving web portion, that is, prime side will remain prime side after handling. At least one of the two turning rods can be shifted transversely to the arriving web, so that lateral offset of the traveling web is possible, within some limits.
For proper paper handling, the web should be wrapped about each one of the turning rods by precisely 180.degree. in order to obtain precise deflection of 90.degree.. Some offset, then, will necessarily arise when parallel turning rods are used. This offset cannot be avoided. The minimum offset of turning rods which are precisely above each other will be EQU 0.5.multidot..sqroot.2d,
wherein d is the diameter of the turning rod.